1. Field of the Invention
The present invention relates to a technique to correct a smear which is contained in an image captured by an imaging apparatus.
2. Description of the Related Art
When a high luminance object is captured by a charge coupled device (CCD) sensor, a phenomenon named smear, in which a bright strip line appears in a vertical direction of a captured image, may occur. When the smear occurs, the image quality of a captured image is reduced. In order to prevent occurrence of the smear, a method has been adopted, which determines the amount of smear from an output level of a vertical optical black (OB) that is a shielded pixel area outside an effective pixel area, and a dummy pixel area having no sensitivity to light, and subtracts the amount of smear obtained by an image signal.
However, recently, owing to a higher pixel density of the CCD sensor, a pixel size has increasingly shown a tendency to be minimized and also an image reading time tends to increase. Thus, a smear occurs even when a low-luminance object is imaged, which has heretofore never caused a problem. Further, when a high luminance object such as the sun is imaged, an unimaginable strong smear occurs, which has not been conventionally considered.
An imaging signal processing apparatus discussed in Japanese Patent Application Laid-Open No. 4-280579 is configured to correct smear by controlling a gain of a luminance gamma correction circuit and a gain of a color difference signal without subtracting a smear signal. Further, a digital still camera apparatus discussed in U.S. Pat. No. 3,788,393 is configured to correct smear by detecting the amount of smear from a plurality of images in order to reduce a weak smear signal.
However, the imaging signal processing apparatus discussed in Japanese Patent Application Laid-Open No. 4-280579 cannot achieve a sufficient correction effect when correcting a large smear signal.
Further, the digital still camera apparatus discussed in U.S. Pat. No. 3,788,393 has a smear occurring in a moving image, and strong smear cannot be reduced.